There have been reports of an issue in which the error “Subtask CheckPrereqs execution failed: Check Tenant Prerequisites” is received when running Hybrid Configuration Wizard. Microsoft recently released a fix to remediate impact.
When you use the Hybrid Configuration wizard to create or manage a hybrid environment that contains Microsoft Exchange Server 2013, you receive the following error message:
Subtask CheckPrereqs execution failed: Check Tenant Prerequisites
Deserialization fails due to one SerializationException:
Microsoft.Exchange.Compliance.Serialization.Formatters.BlockedTypeException: The type to be (de)serialized is not allowed: Microsoft.Exchange.Data.Directory.DirectoryBackendType
This problem occurs because of recent changes to Exchange Online that prevent the Exchange 2013 Hybrid Configuration wizard from running correctly.
Download and install the latest cumulative update for Exchange 2013.
Hybrid Exchange 2013 Server Configuration Validation
1. From the Exchange 2013 PowerShell run Test-FederationTrust –userIdentity firstname.lastname@example.org The output should look like the one below.
2. From the Exchange 2013 PowerShell run Test-FederationTrust –userIdentity (Onpremiseuser@domain.com). The output should be similar to the above.
3. Now run Get-Organizationrelationship |FL to check the Organization relationship and the output should look like the screenshot below.
4. Connect to Office 365 using the following script:
5. From Office 365 PowerShell, verify the TargetSharingEpr field is populated.
6. Once both servers are updated verify to see if you are able to view the free/busy information between the on-premise users and cloud users.
7. If you are still not able to do so, then you should run the Hybrid configuration wizard following the steps below:
8. Check to see if you are able to view Free/busy information.